This invention relates to a process for preparing .alpha.-thujene.
.alpha.-Thujene is the typical starting material from which sabinene hydrate, known as a useful flavor component, is prepared. One of the prior art processes for preparing .alpha.-thujene is the isomerization of sabinene in the presence of ethylenediaminolithium which is obtained by the reaction of lithium with ethylenediamine (see, for example, Shrinivas P. Acharya et al., J. Org. Chem., 34, 3015 (1969) and Alberto Ferro et al., Helv. Chim. Acta., 57, 1152 (1974)).
Such a prior art process, however, has the disadvantage that isomerization of sabinene into .alpha.-thujene is accompanied with a relatively large amount of by-products such as p-cymene. It is troublesome to isolate .alpha.-thujene from such a reaction mixture. If the reaction mixture is directly used without isolation of .alpha.-thujene at this stage as a starting material for the synthesis of sabinene hydrate, troublesome isolation must be done at an intermediate or final stage. In either case, these working problems result in reduced yields of .alpha.-thujene or an end product available from .alpha.-thujene.